How to design an egg timer circuit?

Thread Starter


Joined Feb 15, 2005
Hi, my name is joseph, and i need to hand in a paper on an egg timer circuit by next week. I'm kinda stuck here. I need to design a test circuit that will illuminate an LED for 180 seconds (3minutes) after a switch has been asserted. This circuit as given in the question should incorporate 74LS163 counters plus any other logic/flip-flops that may be required with a clock supplied at 1 Hz using a 555 timer.

I already have the 555 timer circuit that supplys a 1 Hz frequency but the problem is i'm unable to design the circuit with 74LS163-s and flip-flops. Can anybody help me please! I'm really desperate. I can't find the design of this circuit.

Pls help me, email me directly at if there's anyone out there kind enough to help me. Site links to this circuit diagrams or diagrams of the circuit itself will be much appreciated. Thank you.

Joseph :(


Joined Apr 20, 2004
The data sheet on LS163's shows everything there is about those counters, including how to cascade them. Remember that those counters are binary, so you will have to use external gates to decode for 180d (the hexidecimal equivalent of 180 decimal).

If you're really stuck, start a bit smaller. Get a 16d second timer going with only one LS163. If you get that going, go for 12d seconds. That will show you how to decode a short count (hint - use an AND gate to signal when the count = 12d, or Ch).